The change was prompted by deepening drought conditions and new directives by the state government, according to the water authority.

The water authority says stronger conservation measures will help San Diego County keep as much water as possible in storage for next year and comply with emergency water conservation mandates approved last week by the state Water Resources Control Board.

The agency does not expect cutbacks in imported water supplies this year that would trigger mandatory supply cutbacks by member agencies. Reductions could happen next year if conditions don't improve, water officials said.

Maureen Stapleton, the agency's general manager, has said the region was able to avoid mandatory restrictions but the ongoing drought makes that impossible now.

"Regional investments and a demonstrated commitment to conservation have buffered San Diego County from the worst effects of the drought so far, but we believe the right thing to do now is to move to mandatory water conservation measures," Stapleton said. "We don't know how long this drought will last — and the unusually hot and dry conditions have made it more challenging to save water with voluntary efforts."

The new state restrictions follow reports that levels at reservoirs throughout California are continuing to drop.